A generation of behavioral genetic research has convincingly established the existence of a genetic influence on risk of alcoholism, at least in males. Nonetheless, relatively little is known about the nature of that influence, nor how genetic factors might interact with psychosocial experience in the etiology of alcoholism. Over the past 6 years, the principal investigator has been involved in the initiation of several large prospective studies of adolescent twins and adoptees with the overall aim of identifying genetic and environmental influences and interactions in the development of alcoholism. In particular, the conceptual model that guides his research, the model he seeks to develop and test with RSDA support, assumes that the genetic diathesis which can be ultimately expressed as alcoholism in adulthood, is expressed in pre- adolescence and adolescence as personality deviations along two broad dimensions of personality: Behavioral Constraint and Negative Emotionality. Genotype-environment correlation is hypothesized to be the mechanism underlying transition from adolescent personality to adult psychopathology. That is, familial and extrafamilial experience is, in part, influenced by inherited dispositional characteristics, and in turn these experiences, in part, influence subsequent psychological development. Analysis of the extensive behavioral genetic data sets available to the PI will allow him to fully explore this conceptual model.